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Problem : f (x) = 2x. Find f'(x)

Problem : f (x) = - x^{2}. What is the f'(x)?

Problem : Find the slope of the line perpendicular to the tangent of the graph of f (x) = - x^{2} at x = 1.

Problem : Find f'(1) for f (x) = - x^{2} without solving for f'(x) first.

Problem : Give an example of a function that is not differentiable at x = a.